The focus of these studies has been on the functional role of the MHC class I molecule and the development of model systems for examining this function in vitro. Specific accomplishments during the past year include: 1) the characterization of proteolytic pathways involved in the extracellular processing of different class I restricted peptides; 2) the characterization of the minimal peptides derived from the HIV-1 gp 160 envelope glycoprotein that are presented by both H-2Dd and I-Ad; 3) the biochemical and functional analysis of a set of single chain class I molecules generated by engineering techniques; 4) the evaluation of the role of the MHC class I molecule H-2Dd in the signalling of a subset of NK cells bearing the cell surface marker Ly-49; 5) the evaluation of T cell receptor/class I interactions.